Baldern, medieval castle site, Medieval castle ruin in Stallikon, Switzerland.

Baldern is a castle ruin located on the Albis ridge at 810 meters elevation in a densely forested setting. The site consists of earthwork remains with no visible above-ground stone structures.

Baldern Castle probably originated in the 11th century, possibly under Duke Ernest II. In the 12th century it was owned by the Counts of Lenzburg. Whether it survived into the 13th century is unclear, though a noble suffix de Baldern is recorded for the later 13th century. A memorial plaque at the site names 1268 as the year the Zürchers destroyed it, a date based on a confusion by chronicler Heinrich Brennwald.

The name Baldern refers to its role as a medieval fortification in the region. Today visitors walk through a wooded ridge where subtle earthwork remains hint at how people once occupied this hilltop location.

The site lies on the panoramic footpath from Uetliberg to Felsenegg, about 500 metres north of the upper station of the Adliswil-Felsenegg cable car at Felsenegg. The earthworks are obscured by woodland, so allow daylight to distinguish the two ditch-separated areas of roughly 40 by 40 metres and 74 by 45 metres.

The memorial plaque at the site names 1268 as the year the castle was destroyed by Zurich, but this rests on a confusion by chronicler Heinrich Brennwald, who around 1510 linked Baldern to the Regensberg feud of 1267/8. Joseph Eutych Kopp had already doubted the castle's existence in 1847.